This invention relates to an inertial force, accommodating resistance exercise device and method. More specifically, this invention relates to a device and method for generating an opposing force to exercise a user with accommodating resistance primarily through a controlled effort employed by a user of the instant device to overcome inertia of a mass in translation when the device is repeatedly accelerated and decelerated during surface oscillations.
Exercise devices have in common the necessity of enabling a user to experience an opposing force in order to provide resistance to the muscles of the body for the purpose of exercising. This necessity is predicated upon Newton's third law of motion which states that for every force that is exerted by one body on another, there is an equal and opposite force exerted by the second body on the first. The muscles of the body and an exercise device demonstrate the application of this law in an action/reaction combination during the performance of exercise.
With respect to the reaction half of the combination, exercise devices have in the past been designed to take advantage of a variety of forces. Gravity force devices are designed to cause a user to move weight against an opposition provided by the force of gravity, as in the case of barbells or a universal gym. Resilience force devices are designed to cause a user to deform an object such as a spring or elastic band whose resilience properties oppose action by the exerciser. Pneumatic force devices are designed to cause a user to compress or exhaust air in a chamber in order to create opposition, as in the case of most rowing machines. Rotational inertia force devices are designed such that a user experiences resistance when rotation of a metal disk or a flywheel is initiated, as in the case of Nordic ski machines. Friction force devices are designed to cause a user to overcome friction of two interacting surfaces such as between a strap and a flywheel of an exercise cycle. Mechanically-determined force devices are designed to cause a user to overcome the resistance of levers or cables as determined by a speed governor, as in the case of a Cybex machine or a Mini-Gym.
By taking advantage of such forces, exercise devices in the past have enabled a user to perform three basic types of exercise: isotonic, isometric, and accommodating resistance.
Gravity force and resilience force devices are generally used to perform isotonic exercise wherein a muscle shortens and lengthens with varying tension while overcoming and releasing a constant load. In isotonic exercise, the weight or resistance used to exercise is limited to the force that can be overcome at the position or angle where the muscles are weakest in a range of motion. The tension on the muscle is maximal only at that position or angle. In this type of exercise, the speed of motion is relatively slow compared to the rapid movements needed for many sports activities.
Gravity force and resilience force devices are also suited to perform isometric exercise wherein a muscle is given static tension by holding the device in a fixed position. This type of exercise is also commonly performed by pressing against any immovable object. In isometric exercise, there is no motion, and significant gains in strength are specific only to the particular angle or position chosen for the contraction of the muscle.
Exercise devices which take advantage of pneumatic force, friction force, mechanically--determined force, etc., are generally used to perform accommodating resistance exercise (also referred to as isokinetic exercise). In accommodating resistance exercise tension on a muscle varies in direct proportion to the effort expended by the user and is controlled rather than being predetermined by a fixed resistance. Accommodating resistance exercise allows for maximum contraction or tension of a muscle at all joint angles over a full range of joint motion used to perform the exercise and also allows for the speed of movement required for various sports activities to be duplicated by teaching a more efficient activation of muscles by the nervous system. Accommodating resistance exercise, as the basis for a training program, has been rated by many as being superior to isotonic and isometric exercise with respect to rate of strength gain, rate of endurance gain, strength gain over a range of motion, adaptability to specific movement patterns, least possibility of injury, and skill improvement.
In using exercise devices which have been designed to provide accommodating resistance, minimum resistance is experienced when a speed of operation is slow and a greater resistance is experienced when a speed of operation is increased. These devices allow the body to work hard in positions where the body is structured to do hard work and to ease off in positions where the skeletal-muscular system is weak. Rowing machines which employ a pneumatic force to provide opposition, exercise cycles which employ rotational inertia and friction forces to provide opposition, and a Cybex machine which employs a mechanically-determined force to provide opposition are examples of exercise devices which have been designed to take advantage of various opposing forces to enable a user to perform accommodating resistance exercise.
Although machines known in the past have achieved a degree of user acceptance in accommodating resistance training, it would be desirable to create an exercise device capable of taking advantage of an inertial force which is the result of rectilinear or curvilinear translation of an object in order to perform accommodating resistance exercise routines. This type of inertial force is the resistance of an object due to its inertia when the object is accelerated linearly without rotation. (Hereafter, reference to an inertial force will mean an inertial force which is the result of translation of a mass. An inertial force which is the result of rotation of a mass will be so designated.)
An exercise device designed to take advantage of an inertial force is predicated upon what is perhaps the most fundamental property possessed by all objects--inertia. The inertia of an object is a measure of the difficulty in changing the state of rest or motion of the object.
The principles which provide the theoretical basis for an exercise device which enables a user to create and overcome an inertial force to perform accommodating resistance exercise are expressed in Newton's first and second laws of motion. The first law is sometimes referred to as the law of inertia and states that a body continues in a state of rest or motion in a straight line unless it is compelled to change that state by an external force exerted upon it. In other words, because objects possess inertia, an object at rest tends to remain at rest, and an object in motion tends to remain in motion. If the state of rest or motion of an object is altered (start, stop, change direction), a force is needed to accelerate/decelerate the object.
The relationship between an object, force, and acceleration may be expressed in Newton's second law of motion which states that a body acted upon by an external force undergoes an instantaneous acceleration proportional to and in the direction of the force applied to the body. According to this law, the magnitude of force for a given acceleration depends upon the inertia of the object as measured by the object's mass. Simply expressed, the force "F" required to give a mass "m" an acceleration "a" is proportional to both "m" an "a", or F=ma.
As previously noted, Newton's third law states that the action of a force to cause acceleration results in a reaction of an equal and opposite force. This reaction force is an inertial force. The equation, F=ma, indicates that the magnitude of the inertial force can be modified by varying the size of the mass, while the rate of acceleration remains constant. It indicates the inertial force can be modified by varying the rate of acceleration while the size of the mass remains constant. Controlling the rate of acceleration causes the resistance offered by the inertial force to be accommodating.
An exercise device created to utilize inertial force to provide accommodating resistance would be particularly appropriate for physical conditioning and sports training because inertial forces are commonly experienced in moving one's body and in giving motion to external objects. Inertial forces in physical activities are easy to distinguish by the requirement that they come into existence when initiating, maintaining, and terminating motion. Inertial forces provide the predominant resistance when one gives motion to external objects in activities such as throwing or kicking a ball, swinging a racket or bat, blocking or tackling a player in football, etc. They provide the predominant resistance when one gives rapid motion to one's body or its parts in activities such as jumping, leaping, running, swimming, skating, etc.
One of the benefits of inertial force training has to do with the development of cardiovascular or aerobic fitness. Aerobic fitness is the ability of the heart, blood, and blood vessels to transport oxygen to muscle cells, process the oxygen in those cells, and carry off the resulting waste products. Aerobic fitness is considered by many to be the most important component of overall fitness. Physical activities which produce strong, opposing inertial forces through the rapid motion of one's body advantageously inprove and sustain aerobic fitness.
Inertial forces are involved in most popular physical activities used for cardiovascular development. In running, they are involved in accelerating from a stationary position, in the swinging of the arms and legs, and in the dynamics of landing and takeoff as the body is propelled across a surface by the legs. In swimming, inertial forces are generated in overcoming the inertia of the body in the water, in swinging and kicking the legs, and in overcoming the inertia of the water in repeated stroking and kicking. In rowing, inertia is involved in overcoming the stationary position of a boat, in the resistance offered by the mass of oars, and in overcoming the inertia of water with the oars as the boat is rowed.
In a physiological manner similar to the above popular physical activities, an inertial force exercise device would advantageously contribute to aerobic fitness by featuring an opposition of inertial force in exercises which are continuous and rhythmic and which involve a user's major muscle groups. The use of such a device is further analogous to engaging in aerobic activities such as described above in that the strength of the inertial force can be controlled by varying the rate at which actions are performed, thereby making possible a relatively long--duration participation essential for aerobic conditioning. The aerobic benefit from a device which provides for accommodating resistance is in contrast to an exercise device which solely uses a noninertial force, such as gravity, to create an opposing force required for exercise wherein the weight being lifted is constant.
In addition to aerobic benefit, another benefit has to do with the development of flexibility. Flexibility is the range of motion possible at the joints. Joint flexibility is an important element of general health and physical fitness. Adequate flexibility is desirable for all individuals and is considered to be a possible preventor of low back pain and some of the aches and pains that accompany aging. In addition, improved performance in many sports activities and the prevention of injury and soreness can result from an appropriate program of flexibility development. Flexibility is joint and activity specific. Physical activities which require the greatest range and frequency of movement about a joint and which require significant effort to overcome inertial forces in accomplishing the movement are those which contribute most to flexibility. In this regard, swimming, handball, squash, Nordic and Alpine skiing, and tennis are rated very highly. Therefore, the creation of an inertial force exercise device would provide the user opportunities to contribute to the flexibility of the joints of arms and legs through the opposition of inertia to muscles, ligaments, and tendons. Swinging and reaching motions would closely approximate the rapid motions in the physical activities rated highly for their contribution to flexibility.
Still another benefit of inertial force training has to do with the development of muscular strength and endurance. Muscular strength is the amount of force that can be exerted by a single contraction of particular muscles. Muscular endurance is the length of time an activity can be sustained by particular muscles. Developing and maintaining muscular strength and endurance is best achieved by physical activities which permit the maximum contraction of effort of a muscle through the full range of joint motion and which permit the contraction to be repeated. Physical activities, particularly those which involve rapid and repeated motion by the limbs of the body or which involve the limbs to give rapid and repeated motion to external objects, permit the full exertion of the body's muscular capacity in overcoming the inertia of the limb or the limb in combination with an external object. Therefore, physical activities that overcome strong inertial forces provide a means of increasing and sustaining muscular strength and endurance in a way considered to be most desirable.
Examples of activities which permit a maximum and repeated contraction of a muscle or muscle group through a range of motion required to perform the activity include swimming, wherein the limbs may experience maximum resistance from the water; rowing, wherein maximum resistance may be experienced from the water through the oars; skating, wherein the legs may experience maximum resistance in pushing off against a surface; boxing, wherein the arms may experience maximum resistance in swinging and striking; etc.
Physical activities such as described above permit a maximum contraction of muscles through a specified range of motion because the resistance provided by inertial forces is accommodating. The magnitude of the inertial force, or opposing force is dependent on the acting force of the body. That is to say, the resistance experienced by the muscles at any point during an acceleration will be dependent upon the force the muscles are able to exert at that point. The resistance is accommodating in proportion to the changing muscular capability at every point in the range of motion. Accommodating resistance during these activities allows all muscles and muscle groups, irrespective of their relative strength, to undergo maximum contraction during an entire range of motion and for these contractions to be repeated, thereby providing for muscular strength and endurance. Accordingly, it would be highly desirable to create an exercise device which would enable a user to experience the same opportunities to develop and maintain muscular strength and endurance through accommodating resistance offered by an inertial force as physical activities such as those described above.
The invention which is the subject of the instant patent is a device of a mass translation type which has been created primarily to take advantage of translational inertial force as the opposing force necessary for accommodating resistance exercise to provide the benefits described above having to do with developing and maintaining aerobic fitness, flexibility, muscular strength, and muscular endurance.
The subject invention falls in the category of surface--operated exercise devices which are generally rolled on a surface to perform exercises.
In the past, inventions in this category have most often been designed to take advantage of gravity as the means of establishing the opposing force necessary for exercise. One design comprises a single wheel on a shaft. Another design comprises two double-wheeled, foot-mounted devices. Other designs comprise rollable devices--one for each hand--with unique features such as the use of tracks, the use of brakes, the use of resistance springs, the use of casters, etc. Gravity becomes the opposing force as these devices are used in performing exercise to support, raise, or lower the body of the user in relation to the surface.
In addition to taking advantage of gravity as the opposing force, other inventions in this category have been designed to take advantage of the resistance offered by the inertia of a rotating mass. One design comprises two disk-shaped weights as the wheels of the device. Another design comprises spherically-shaped, rotatable weights as the means for rolling the device.
These previous inventions in the category of surface-operated exercise devices require a significant downward force vector to be applied and maintained as a user exerts effort to support the weight of the body and/or to overcome the rotational inertia of the weighted rotating members. This requirement limits the range of exercise that may be performed and the benefits that may be derived therefrom. It limits the freedom and rapidity with which these devices may be moved on a surface. It limits the community of users to those already in the possession of sufficient upper body strength to exert the pressing force required to support the body weight in various attitudes and positions and to rotate mass and to change the direction of rotation.
The difficulties suggested in the preceding are not intended to be exhaustive, but rather indicate a lack of appreciation in the prior art for significance of surface-operated, inertial force exercise devices and methods. Other noteworthy problems may also exist; however, those presented above should be sufficient to demonstrate that surface-operated exercise devices and methods, which use only gravity and/or the inertia of rotating mass as a means of establishing opposition, will admit to worthwhile improvement.